1. Field of the Invention
The present invention relates to a method of and an apparatus for angular velocity detection.
2. Related Background Art
A vibration gyro is known as one of means for detecting an angular velocity. Based on the principle that "a Coriolis force is produced when an angular velocity is applied to an object with a velocity", the vibration gyro adds a vibration to the object to cause it to have a velocity, receives the Coriolis force produced when an angular velocity is applied to the object, and detects the Coriolis force proportional to the angular velocity entered as a displacement of the spring system, thus detecting an angular velocity applied to the object.
An object of this vibration gyro which applies a vibration, that is, a vibration member is available in a shape of a tuning fork or a H-shape. However, the conventional vibration gyro has a single vibration member with a structure which permits mere detection of rotation in a plane and an angular velocity applied to the object.
In detection of the angular velocity of a camera or other moving object on which the above conventional single-axis type vibration gyro, not only a one-dimensional angular velocity component but also two-dimensional and three-dimensional components are generally produced from the moving object. Therefore the conventional vibration gyro which has only been able to detect the angular velocity in a single-axis direction is not suitable for precisely detecting the angular velocity.
Hence various types of vibration gyro capable of detecting angular velocities of two-axis direction components have been proposed. This two-axis type vibration gyro has been disclosed in Japanese Patent Application Laid-open No. 63-61114, No. 64-16911, No. 1-140013, No. 2-198315, No. 2-218914 and No. 4-25714.
FIG. 22 shows a vibration gyro disclosed in Japanese Patent Application Laid-open No. 64-16911.
The conventional vibration gyro shown in FIG. 22 is adapted to have H-shaped vibration members 1 and 2 which are assembled to orthogonally intersect each other, apply an AC voltage to piezoelectric elements 4 and 5 connected to the sides of respective vibration members 1 and 2 to vibrate these vibration members 1 and 2 to give a velocity, and detect a distortion of the Coriolis force in two axial directions as electro-mechanical conversion signals from piezoelectric elements 6 and 7 connected to two orthogonally intersecting sides of a square support bar 3 which is extended in the Y direction, thus obtaining the angular velocity,
The above other related arts employ a structure which is basically a combination of two vibration systems.
The above-described related art vibration gyro includes a problem that it has required two vibration systems and the drive and detection circuits respectively for the vibration systems and therefore it has been inevitably complicated in construction and large-sized in the electric circuit,
Most examples of the related arts include a problem that displacement is small and the output level of detection signal is low since a vibration caused by the Coriolis force is not a resonance vibration.